Dictionary attack

technique for defeating a cipher or authentication mechanism by trying to determine its decryption key or passphrase by trying hundreds or sometimes millions of likely possibilities, such as words in a dictionary

A dictionary attack is a method used in cryptography to find a key (or username, or password). A large number of words are tried. These words usually come from a special collection, called a "dictionary".

The attack is based on trying all the strings in a pre-arranged listing. The listing is usually derived from a list of words, such as in a dictionary (hence the phrase dictionary attack).[1]